Propulsion of a person by means of a balancing vehicle entails two components: The first is that of supplying power to effectuate locomotion, while the second is that of maintaining balance. Balance, as used herein, refers to maintaining stability in the fore-aft plane (defined, in turn, by the direction of motion and the vertical). The functions of propulsion and of balance are typically provided either by the user (as in the case of a unicycle, for example) or by a motor in conjunction with a controller (as in the case of the human transporter described in U.S. Pat. No. 5,701,965, which is incorporated herein by reference.)
While specialized skills are typically required for a person to maintain fore-aft balance on an unstable vehicle, only a small portion of the power exerted to achieve locomotion is necessary for the balancing function. Such skills are not trivial and often become diminished with age. Consequently, supplementing the balancing ability of a rider is a desirable aim.